New research sheds light on how to help birds in the vanishing Atlantic Forest

The Atlantic Forest is one of the most threatened ecosystems on the planet, with just 3.5 to 5 percent of its original forests remaining.

Researchers found that mature forest boasted the most threatened and endemic species, but secondary forest also provided important habitat.

They recommend placing more conservation attention on mature and secondary forests, and better protecting what’s left of the Atlantic Forest by creating more conservation corridors to connect existing protected areas.

South America’s Atlantic Forest is one of the most imperiled biomes on the planet. At its southern periphery in northeastern Argentina’s Misiones province, the country’s first ecological corridor links important protected areas within the Atlantic Forest region. A new study looks into the bird diversity of different types of Atlantic Forest habitats, finding that mature forest beat out secondary forest and grassland in terms of bird diversity. However, it also finds that secondary forest still contained relatively high bird diversity, and provided valuable habitat for threatened species. Its authors underline the conservation importance of mature forests, and urge their protection as well as the maintenance and creation of corridors that knit together protected areas.

Hundreds of years ago, the Atlantic Forest was a vast tract of forest that stretched down the coast of Brazil and into Paraguay and Argentina. Today, it is one of the world’s most threatened biodiversity hotspots, facing severe pressures from human activities like logging and farming that has left the biome severely fragmented. Studies estimate only 6 to 10 percent of the Atlantic Forest remains, and its primary forest has dwindled down to 3.5 to 5 percent.

Conservationists say restoration and maintaining connectivity between forest fragments is crucial to sustaining viable populations of the many species that depend on the Atlantic Forest to survive. The authors of the study published this week in Mongabay’s open-access journal Tropical Conservation Sciencealso underline the importance of evaluating the impacts of different habitat types on wildlife diversity.

Misiones Province (outlined in green) contains the only Atlantic Forest in Argentina. However, data from Global Forest Watch show human activities are dramatically affecting it, with the province losing nearly 14 percent of its tree cover from 2001 through 2014. Satellite imagery shows clearings and tree plantations abutting forest.

They focused their study on birds in Misiones province, which has the highest number of bird species in Argentina.

“There are approximately 548 bird species, of which 187 are found only in this province,” primary author of the study Flavia Barzan told mongabay.com. “Some of them have a special value due to their specific ecological or habitat requirement, their threatened status (at both national and global levels) or their endemic level.

Specifically, the study took place at the Ecological Corridor Urugua-i-Foerster, a 1,500-hectare area that consists of both public and private protected areas, as well as agricultural land with small cultivated plots. The corridor consists of three main habitat types – mature forests, secondary forests and grasslands – that are in different stages of restoration. The researchers looked at four different groups of bird species: forest specialists, which are mostly found deep within forests; generalists, which can live in a variety of habitats; edge species, which live at the interfaces of forest and open areas; and grassland specialists, which are only found in open areas.

The corridor was created to preserve and restore the connectivity between the provincial parks and offset the harmful effects of roadways, which are bringing increased urbanization, deforestation, fragmentation and resource extraction into the region, the study explains. The goal of this corridor is to restore native humid forests in areas that were deforested for agricultural and timber extraction purposes, and to create a habitat bridge between protected areas.

“Although the creation of ecological corridors for…conservation management is a strategy that was developed in theory a few decades ago, their implementation in environmental politics is very poor yet, especially in Argentina, where habitats’ conservation are in their beginnings,” Barzan said. She added that the situation in other South American countries is similar and that is probably why there has been a lack of research on the topic. She said this study tries to show “that it is possible to connect habitat fragments and restore both habitats and connection between them.”

Mature Atlantic Forest once covered about 80 million hectares in Brazil, Paraguay, Argentina. Today, only around 5 percent remains, making it one of the most threatened regions in the world. Photo by Flavia Barzan.The grasslands the researchers studied are areas that have been deforested by human activities – namely to create pasture for livestock. In the corridor, this habitat is under ecological recovery. Photo by Flavia Barzan.The secondary forest habitat type the researchers looked at consists of shrubs and trees that are among the first to grow during the intermediate stage of recovery. Photo by Flavia Barzan.

The researchers found that mature forests displayed the highest levels of bird diversity, followed by secondary forests and then grasslands. Grasslands contained grassland specialists and edge species, and showed very low similarity to mature forests.

In addition to Misiones supporting Argentina’s highest bird diversity, the province is also home to many species that are threatened or endemic – which means they are found nowhere else in the world. In total, the researchers recorded 123 different species. Of these, 104 were found in mature forests, 45 in the secondary forests and 20 in the grasslands. They observed 33 endemic species, of which 27 are forest specialists and three are both endemic and globally threatened – the helmeted woodpecker (Dryocopus galeatus), blackish-blue seedeater (Amaurospiza moesta), and southern bristle-tyrant (Phylloscartes eximius). The researchers recorded 53 percent of the forest specialist species in mature forests, higher than in secondary forests where forest specialists occurred at only 33 percent and generalists were more the norm.

Previous research on how anthropogenic activities cause forest fragmentation and habitat loss have shown that the most altered habitats have low bird richness, with more generalist bird species and non-forest-dependent species. Forest-dependent, endemic and threatened bird species are strongly affected by fragmentation, according to the authors of this study.

The helmeted woodpecker (Dryocopus galeatus) is listed by the IUCN as Vulnerable, and is endemic to the Atlantic Forest. Photo by Jorge La Grotteria.

“Studying the relationships and the factors that determine the structure and composition of bird communities provides helpful information about the alteration of the environment and species populations by human activities,” the study says.

The authors write that local diversity is indicative of regional diversity, and that their findings could be used to help evaluate the statuses of bird species outside the ECU-F corridor.

“Although this study was conducted at a local level and represents a small area of the Atlantic Forest, our results have implications for future conservation plans in other areas of the Atlantic Forest ecoregion,” the study says. “Our results confirm the great need for conservation of both secondary and native forest in this area and other tropical forest fragments of Atlantic Forest subjected to anthropogenic activities such as selective logging and agriculture.”

The saffron toucanet (Baillonius bailloni) is a resident of the Ecological Corridor Urugua-í –Foerster. It is listed by the IUCN as Near Threatened globally, and as Threatened in Argentina. Photo by Julián Baigorria.

The study found mature forests are important reservoirs of bird diversity and they also tend to be highly threatened by human activities. Because of this, it recommends that mature forests (as well as forests in other stages of recovery) should be given particular consideration in Atlantic Forest management plans.

The researchers also underline the importance of creating and maintaining connected protected areas like the ECU-F corridor.

“Proper design of ecological corridors, with suitable habitat conditions and free circulation of wildlife and native vegetation, may ensure the preservation of biodiversity in the Atlantic Forest and its environmental services in the medium and long term,” they write.